On the market existing constructions of this type consist of oil recover units, which are used for the clearing of oil and the separation of water from the oil for e.g. in oil spills in watercourses near beaches, from the surface of water, inside tankers and other places. The oil recover units of today are large, expensive, with complicated structure, ungainly to manage, it therefore takes time to get these in place to get the work done immediately. Large oil recover units do not reach to work over all places, since the environment does not allow for their use or because they take too much space and are too heavy. This is the reason why much of the cleaning up work to separate the oil is done by hand with pitchforks, spades, rakes etc. Previous methods retrieve the oil/water mixture in a container, whereupon one must wait 10-20 hours for the oil to rise to the surface so that the oil then can be removed. This takes time and requires large space and has no continuity in the process. Document U.S. Pat. No. 4,855,065 shows a very large, expensive and complicated structure for the separation of oil from water with mobile parts. Through many stages and by centrifugalizing the water/oil mixture the water can be separated. Document U.S. Pat. No. 2,917,178 shows another large, ungainly and expensive machine using a complicated process, where the water/oil mixture pours through different rooms and sections in stages, transported from above downwards, the oil being separated from the water and finally filtered through a filter. In document U.S. Pat. No. 1,984,003 the separation of water from oil takes also place in different stages through to a number of different rooms and sections. This installation shows mainly the same disadvantages as those in the other two documents show. Furthermore the above installations also require high maintenance, which is costly.